CVE-2026-33159: Craft CMS Unauthenticated Users Can Perform Restricted Vulnerability

MODERATE
Advisory Identifier: GHSA-6mrr-q3pj-h53w
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CWE-306 CWE-862
Published
Advisory Summary

CVE-2026-33159 is a MODERATE unauthenticated users can perform restricted vulnerability (CWE-306: Missing Authentication for Critical Function) affecting Craft CMS libraries in the Packagist ecosystem. The issue involves unauthenticated users can perform restricted project config sync operations. Remediation is available by upgrading affected packages to version 5.9.14, 4.17.8.

CVE-2026-33159 at a Glance

CVE Identifier CVE-2026-33159
GHSA Identifier GHSA-6mrr-q3pj-h53w
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-306: Missing Authentication for Critical Function
Affected Product Craft CMS
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-33159

To remediate this vulnerability, upgrade all affected Craft CMS dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

craftcms/cms fixed: 5.9.14 
Upgrade craftcms/cms to 5.9.14
craftcms/cms fixed: 4.17.8 
Upgrade craftcms/cms to 4.17.8
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for craftcms/cms

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-33159, inspect your project dependencies for Craft CMS:

inspect dependencies for craftcms/cms

Analyze the terminal output to locate any version of Craft CMS in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.9.14), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-306: Missing Authentication for Critical Function, where the product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. In Craft CMS, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary Guest users can access Config Sync updater `index`, obtain signed `data`, and execute state-changing Config Sync actions (`regenerate-yaml`, `apply-yaml-changes`) without authentication. ### Details `ConfigSyncController` extends `BaseUpdaterController`, and the base updater is anonymously accessible for control panel requests. `index` emits signed updater state (`data`), which can be reused by guests in subsequent requests. Sensitive actions that are reachable via this method are `actionApplyYamlChanges`, `actionRegenerateYaml`, `applyExternalChanges`, and `regenerateExternalConfig`. #### Reproduction steps 1. Guest POST to: http POST /admin/actions/config-sync/index 2. Extract data from returned JS state: Craft.updater = ... setState({"data":"<signedData>", ...}); 3. Reuse data as a guest: ``` POST /admin/actions/config-sync/regenerate-yaml data=<signedData>&<csrfParam>=<csrfToken> ``` or ``` POST /admin/actions/config-sync/apply-yaml-changes data=<signedData>&<csrfParam>=<csrfToken> ``` 4. Observe completed response and state/file changes. ### Impact Unauthenticated users can execute project configuration sync operations that should be restricted to trusted admin/deployment contexts. Depending on the pending YAML/config state, this can cause unauthorized config state transitions and a service integrity risk. ### Resources https://github.com/craftcms/cms/commit/7f0ead833f7

CVE-2026-33159 Affected Craft CMS Versions

2 component(s)
Fixed Versions:
5.9.144.17.8
Product / Package Ecosystem Affected Versions Fixed Version
craftcms/cms
 Packagist
≥ 5.0.0-RC1
< 5.9.14
5.9.14
craftcms/cms
 Packagist
≥ 4.0.0-RC1
< 4.17.8
4.17.8

References

GitHub Advisory / Wiki ADVISORY
https://github.com/craftcms/cms/security/advisories/GHSA-6mrr-q3pj-h53w
NVD — CVE-2026-33159 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33159
Security Fix Commit FIX COMMIT
https://github.com/craftcms/cms/commit/7f0ead833f7c2b91ae12003caad833479dd08592
Craft CMS Source Repository REPOSITORY
https://github.com/craftcms/cms
Craft CMS Release RELEASE
https://github.com/craftcms/cms/releases/tag/4.17.8
Craft CMS Release RELEASE
https://github.com/craftcms/cms/releases/tag/5.9.14

Frequently Asked Questions

What is CVE-2026-33159?
CVE-2026-33159 is a security vulnerability in Craft CMS involving Unauthenticated Users Can Perform Restricted Project Config Sync Operations under CWE-306: Missing Authentication for Critical Function.
Which Craft CMS versions are affected?
Affected versions include releases prior to 5.9.14, 4.17.8 across affected packages: craftcms/cms.
What version fixes CVE-2026-33159?
Upgrading to 5.9.14, 4.17.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is craftcms/cms affected?
Yes, craftcms/cms is affected in releases prior to 5.9.14, 4.17.8. Upgrade your dependency to 5.9.14, 4.17.8 or later.
What CWE is associated with CVE-2026-33159?
CVE-2026-33159 is classified under CWE-306: Missing Authentication for Critical Function (The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.).
How can I check Packagist dependencies for CVE-2026-33159?
Run the dependency tree command: 'inspect dependencies for craftcms/cms'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6mrr-q3pj-h53w",
  "modified" : "2026-03-25T20:59:54Z",
  "published" : "2026-03-24T16:57:17Z",
  "aliases" : [ "CVE-2026-33159" ],
  "summary" : "Craft CMS: Unauthenticated Users Can Perform Restricted Project Config Sync Operations",
  "details" : "### Summary\nGuest users can access Config Sync updater `index`, obtain signed `data`, and execute state-changing Config Sync actions (`regenerate-yaml`, `apply-yaml-changes`) without authentication.\n\n### Details\n\n`ConfigSyncController` extends `BaseUpdaterController`, and the base updater is anonymously accessible for control panel requests.  `index` emits signed updater state (`data`), which can be reused by guests in subsequent requests.\n\nSensitive actions that are reachable via this method are `actionApplyYamlChanges`, `actionRegenerateYaml`, `applyExternalChanges`, and  `regenerateExternalConfig`.\n\n#### Reproduction steps\n\n1. Guest POST to:\n\n    http POST /admin/actions/config-sync/index\n\n  2. Extract data from returned JS state:\n\n    Craft.updater = ... setState({\"data\":\"<signedData>\", ...});\n\n  3. Reuse data as a guest:\n\n```\n  POST /admin/actions/config-sync/regenerate-yaml\n  data=<signedData>&<csrfParam>=<csrfToken>\n```\n\n  or\n\n```\n  POST /admin/actions/config-sync/apply-yaml-changes\n  data=<signedData>&<csrfParam>=<csrfToken>\n```\n\n  4. Observe completed response and state/file changes.\n\n### Impact\n\nUnauthenticated users can execute project configuration sync operations that should be restricted to trusted admin/deployment contexts.\n\nDepending on the pending YAML/config state, this can cause unauthorized config state transitions and a service integrity risk.\n\n### Resources\n\nhttps://github.com/craftcms/cms/commit/7f0ead833f7",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.0.0-RC1"
      }, {
        "fixed" : "5.9.14"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.9.13"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0-RC1"
      }, {
        "fixed" : "4.17.8"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.17.7"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/security/advisories/GHSA-6mrr-q3pj-h53w"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33159"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/commit/7f0ead833f7c2b91ae12003caad833479dd08592"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/craftcms/cms"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/releases/tag/4.17.8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/releases/tag/5.9.14"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-306", "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-24T16:57:17Z",
    "nvd_published_at" : "2026-03-24T18:16:09Z"
  }
}